Generally, a power storage device such as a secondary battery includes, as main components, a positive electrode, a negative electrode, and an electrolytic solution. In the electrolytic solution, an appropriate electrolyte is added at an appropriate concentration range. For example, in an electrolytic solution of a lithium ion secondary battery, a lithium salt such as LiClO4, LiAsF6, LiPF6, LiBF4, CF3SO3Li, and (CF3SO2)2NLi is commonly added as an electrolyte, and the concentration of the lithium salt in the electrolytic solution is generally set at about 1 mol/L.
In an organic solvent to be used in an electrolytic solution, an organic solvent having a high dipole moment and a high relative permittivity such as ethylene carbonate or propylene carbonate is generally mixed by not less than about 30 vol %, in order to suitably dissolve an electrolyte.
Actually, Patent Literature 1 discloses a lithium ion secondary battery using an electrolytic solution that uses a mixed organic solvent containing ethylene carbonate by 33 vol % and that contains LiPF6 at a concentration of 1 mol/L. Furthermore, Patent Literature 2 discloses a lithium ion secondary battery using an electrolytic solution that uses a mixed organic solvent containing ethylene carbonate and propylene carbonate by 66 vol % and that contains (CF3SO2)2NLi at a concentration of 1 mol/L.
In addition, for the purpose of improving performance of secondary batteries, studies are actively conducted for various additives to be added to an electrolytic solution containing a lithium salt.
For example, Patent Literature 3 describes an electrolytic solution obtained by adding a small amount of a specific additive to an electrolytic solution that uses a mixed organic solvent containing ethylene carbonate by 30 vol % and that contains LiPF6 at a concentration of 1 mol/L. Patent Literature 3 discloses a lithium ion secondary battery using this electrolytic solution. Furthermore, Patent Literature 4 describes an electrolytic solution obtained by adding a small amount of phenyl glycidyl ether to a solution that uses a mixed organic solvent containing ethylene carbonate by 30 vol % and that contains LiPF6 at a concentration of 1 mol/L. Patent Literature 4 discloses a lithium ion secondary battery using this electrolytic solution.